Turning gear for internal combustion engines



1 i v I Feb. 1942- c A. E TURNING GEAR FOR INTERNAL COMBUSTION ENGINESFiled May 10, 1939 Patented Feb. 24, 1942 TURNING GEAR FOR INTERNALCOMBUSTION ENGINES Henry Charles Alexandre Potez, Meaulte, FranceApplication May 10, 1939; Serial No. 272,889

- In France May 1-8, 1938 A 5 Claims.

It is known that the solution of the problem of the starting of aviationengines,'and particularly of touring aeroplane engines, is 'a difficultmatter, owing to the numerous and often contradictory conditions tocomply with. These conditions are as follows:

An entire self-action as the only power available is'that which can befurnished by the tourist or his assistant, without excessive fatigue; areduced size and weight; a low cost price; an easy actuation from thepilots cockpit without being obliged to leave the aeroplane; areliableworking, even in cold weather, and even with an engine having alreadyfurnished a long service, in which the tightness of the valves andpistons may be imperfect for very slow speeds of the crank-shaft, eventhough, this tightness is quite sufficient for normal running; thegreatest possible independence of the parts of the starter and of theengine during the operation of the latter.

,It is shownby experience that the conditions of entire self-action andof reduced fatigue lead to approach as closely as possible theconditions of manual turning of the propeller, at least for the enginesof average power. For this purpose, it has been proposed to turn thecrank-shaft by means of a hand-crank and through the medium ofgear-wheels or by a lever which is connected to the crank-shaft of theengine also by gear- Wheels.

' Such devices have the drawback of obligating the operator to greatefforts, which are in most cases impossible to exert from the pilotscockpit, for the reason that in order to obtain a suf ficient pistonspeed for the proper compression of the combustible mixture in thecylinders, it is impossible to use a great gear-reduction ratio.

The present invention has for its object to provide a turning gear forinternal combustion engines, more particularly aircraft engines of smalland medium power, which complies with the above-mentioned conditions andwhich obviates the aforesaid drawbacks, particularly in that thestarting operation can be carried out from the pilots cockpit withoutleaving the aeroplane, with a force which is as small as may be desired,while ensuring the best conditions of turning, particularly as regardsthe compression and the l ignition.

.The turning gear according to the invention comprises a crank-plate, orlike" device, which is connected on the one hand with means by which itcan be rotated at slow speed, i. e. by using a reduced force, and on theother hand, by means of a suitable speed-reduction gear, to thecrankshaft to be operated, the crank-pin of said plate being connectedwith an accumulator of energy" which stores up the energy duringone-half of a revolution of the said plate and then restores it duringthe other half revolution.

According to a preferred embodiment of the invention, the saidaccumulator consists of one or more springs or like elastic memberswhich are attached at one end to the crank-pin of the crank-plate, andat the other end .to a fixed vention.

Fig. 2 is a partial view of a modification of the turning gear shown inFig. 1.

According to the embodiment shown in Fig.- l, the turninggear comprisesa hand-crank I the shaft 2 of which is rotatable in the casing 3,

and carries the driving member 4 of a freewheel mechanism of any knowntype. The driven member 5 of said free-wheel mechanism is keyed to ashaft 6 together with a ratchetwheel 1 cooperating with a retaining pawl8 adapted to prevent any backward rotation of the shaft 6 which wouldcause a backward motionof the crank I. On shaft 6 there is slidablymounted the driving member 9 of a safety friction clutch. Said drivingmember 9 may be urged by a spring I0 against the driven member ll ofsaid friction clutch.

The said member H is rotatable on the shaft 6, and is connected. inrotation to a loose pinion l2. This pinion l2 meshes with a gear-wheel I3flkeyed to a shaft [4 which is rotatable in the casing 3. plate. Itcarries an eccentric crank-pin I 5, to which is attached an elasticdevice l6 forming an accumulator of energy, which consists, in theembodiment illustrated, of spring means subject to elongation andattached to a pin ll mounted in the casing 3. l, i It will be noted thatthe spring means I 6 is stretched (which corresponds to an accumulationof energy) when'the'crank-pin moves from the position l5 to the positionl5, both of which aresituated in the diametrical plane passing throughthe axes XX and YY of the shaft I4 and the attaching pin IT, but will onthe contrary contract (which corresponds to a very rapid restoration ofthe accumulated energy) when the crank-pin moves from the position l5 tothe position I5 On the shaft M of the crank-plate I3 is secured orformed the driving member l8 of a releasing device. The driven member 20of said releasing device is normally connected in rota- ,tion to saiddriving member I8 by a ball l9;

which is located in two recesses formed in the The gear-wheel l3 forms acrankmembers It and and is clamped between these members by a spring 2|adapted to urge the driven part 29, which is slidably keyed to a shaft22, towards the member I8. A pinion 23 keyed to the shaft 22 engages agear-wheel 24 keyed to a shaft 26 extending out of the casing 3.

The unit A above described, which is preferably independent, is combinedwith a unit B which will be described below, the connection being madeby suitable coupling devices 25 and w an intermediate shaft 26 whichconnects the shaft 25 of the unit A with shaft 21 of the unit B. Shaft21, which is rotatable in the casing 28, is connected to a shaft 29 byacoupling device adapted for automatic or controlled release, whichpreferably provides for the complete uncoupling of the two shafts 21 and29 when the shaft 29 tends to drive the shaft 21.

The said coupling device may, for instance, be realized as illustratedand as known per se.

In the embodiment illustrated, the shaft 21 has a threaded part 36adapted for the longitudinal displacement thereon of a nut 3| which isimpeded in its rotation by a, brake 32. The said nut carries ajaw-clutch disc 33 cooperating with a like disc 34 mounted on the shaft29. Shaft 29 carries a pinion 35 meshing with a pinion 36 keyed to anextension of the crank-shaft 31 of the engine which is to be started.

This engine, having N cylinders, may be of the four-stroke or of thetwo-stroke type, operating with gasoline or with fuel oil. The gearwheels 23, 24, 35, 36 interposed between the crank-plate and thecrankshaft of the engine having N cylinders are so chosen that the ratiobetween the angles described by the crank-plate I3 and the crank-shaft31 during the starting will be equal to in the case of a four strokeengine, or to N in the case of a two-stroke engine, in order that thesuccessive revolutions of the crank-plate shall correspond to thepassage of the successive cylinders of the engine through the same pointof the cycle, for instance to the explosion.

Moreover, the releasing device (I8, I9, 29) which provides for thmomentary release of the crank-plate I3 (or like device) from thecrankshaft 31 in the case of a reverse movement or return of thislatter, as well as the automatic uncoupling device (33, 34), are soarranged that the relative angular positions of the said plate and ofthe crank-shaft will always differ by an angle which is equal to, or amultiple of 4-11 21r TV or R according to the case of a four-stroke or atwostroke engine, and. this in such a way that when the crank-pin I5 ofthe crank-plate (or like deyice) Passes through its dead centre oppositethe The plate I3 will thus actuate through the medium of the releasingdevice (I8, I9, 29) the gear wheels and the automatic uncoupling device(33, 34), the crank-shaft 31 of the engine, at a very slow speed, as thereduction ratio provided by the gearings is very high for reducing theforce to be exerted upon the crank I.

At the same time, the rotation of the, plate I3 causes the storing-up ofa certain amount of energy in the elastic device I6, owing to theincreasing tension of the" spring means, and this will take place duringa time which is as long as desired, i. e., by the effect of a powerwhich is as small as desired. When upon continuation of the rotation ofthe plate I3, the crank-pin I5 moves very slightly past the positioncorresponding to the maximum tension of the spring means I6, which willrestore the accumulated energy to the crank-shaft 31 by means of themechanical connection with said crankshaft and during a time dependingonly on the force of the spring means and the total load torque. Duringthis rotation of the plate I3 under the impulse of the accumulator ofenergy, the hand-crank I is released, as to rotation, from the pinion I2by the free-wheel device (4, 5). a

As the operator continues the manoeuvre, it will be noted that while thecrank I turns with any circular movement, and particularly as slowly asdesired and with any number of times of stopping as may be desired, thecrank-shaft 31 is driven with a movement composed of a slow rotation ina given ratio to that of the hand-crank I, and of rapid angular impulseswhich are imparted to it by the accumulator of energy. It should beremarked that owing to the aforesaid ratio between the rotation of theplate I3 and that of the crank-shaft 31, the impulses can be transmittedto the crank-shaftfor well-defined positions of this latter, and namelyin such a way that the maximum torque produced by the accumulator ofenergy will facilitate the passage of the pistons at the upper deadcentre of the compression stroke.

In the case of a return or backfire of the engine, the clutch 9, II willslip, thus relieving the wheel 1 which is held by the pawl 8 from anyabnormal stress. Moreover, the releasing device I9, I9, 29 can operat inthe case in which the force is quite considerable. As long as the forcedoes not exceed a value determined by the spring 2|, the ball l9provides for the driving of the member 20, while in the contrary case,the said ball is forced out of its recesses and allows a relativrotation between the members I8 and 20. (It is to be noted that thisreleasing device should be placed at the mostfavourable point for theprotection of the parts of the starter.)

The releasing device can be replaced by a member providing for a pliabletransmission of the movement, such as a shaft I4 working by torsion(Fig. 2) which, in the case of return or backfir will afford a moregradual stress upon the clutch 9, II. 3

Obviously, the invention is not limited to the embodiments hereindescribed and represented, which are given solely by way of example.

The member for driving the pinion Il may consist of a small electricmotor having the smallest power that may be desired. In this case, andin order to prevent an excessive instantaneous consumption of current,it is of advantage to still make use of a hand-crank for actuatinginitially the plate I3 by hand, where-,

by the plate, by means of suitable contacts with which it is providedacts, in order to supply current to the electric motor during a predetermined part of the rotation of the plate, and at well-definedintervals. It is thus possible to avoid the supply of current to themotor at the time of the maximum resistance torque of the plate, andalso to take advantage of the inertia effects of a suitable flywheelmounted on the armature of the said electric motor.

The spring means It may be replaced by any other devices which willserve the same purpose, for instance by a piston compressing a fluid, orby any other device adapted to receive from the plate l3 and to storeup, during a rotation 11' of this plate, a certain amount of energy, andto restore this energy as completely as possible to the said plateduring the next rotation 11' which it must make in order to effect acomplete evolution.

The units A and B may be closely combined in order to form a singleunit.

The releasing device (l8, IE, it) may be situated at any point on theconnection between the plate l3 and the shaft 31.

Having now described my invention what 1 claim as new and desire tosecure by Letters Patent is:

1. A turning gear for turning the crankshaft of an internal combustionengine with a view of starting same, comprising operating means, arotatable crank-member in the form of a circular plate carrying aneccentric crank-pin and formed with gear teeth on its periphery, aconnecting means between said operating means and said crank-member forrotating same from said operating means, said connecting means includinga free-wheel mechanism having a driving member connected in rotation tosaid operating means, and a driven member, a ratchet wheel connected inrotation to the driven member of said free wheel mechanism, apawlengaging said ratchet wheel for preventing reverse rotation thereof, afriction clutch having a driving member connected in rotation to saidratchet wheel and a driven member, a toothed pinion connected inrotation to said last-mentioned driven member and meshing with the teethformed on v the periphery of said crank-member, a speed reducingtransmission for connecting said crank member to the crankshaft to beturned and a spring means connected to and cooperating with saidcrank-pin and expanding during one half ofa revolution of saidcrank-member and contracting during the other half revolution of saidcrank-member thereby imparting an additional impulse to said crankshaft.

2. A turning gear as claimed in claim 1, in which said speed reducingtransmission includes an automatic uncoupling device having a drivingmember operatively connected to said crank member and a driven memberand means for operatively connecting said driven member to the crankshaft of the engine, said uncoupling device being such that the drivingand driven members will be uncoupled when the driven member tends todrive the driving member whereby the turning gear is uncoupled from theengine when the latter has started.

3. A turning gear as claimed in claim 1, in which said speed reducingtransmission includes an automatic releasing device having a drivingmember operatively connected to said crank member and a, driven member,and means for operatively connecting said driven member to the crankshaft of the engine, said automatic releasing device being such that thedriving member can drive the driven member for one relative angularposition only of said driving and driven members and that these membersWill be uncoupled when the torque transmitted exceeds a determinedvalue.

4. A turning gear for turning the crankshaft of a four-stroke internalcombustion engine having N cylinders with a view of starting saidengine, comprising operating means, a rotatable crank-member in the formof a circular gear carrying an eccentric crank-pin, a connecting meansbetween said operating means and said crank member for-rotating samefrom said operating means, spring means connected to said crank-pin andexpanding during one half of a revolution of said crank-member andcontracting during the other half revolution of said crank-memberthereby imparting an additional impulse to said crankshaft, a speedreducing transmission for connecting said crank-member to the crankshaftto be turned so that the ratio between the angles described by saidcrank member and said crankshaft during the starting operation will beequal to and uncoupling means inserted in said speed reducingtransmission and so arranged that when these uncoupling means areoperative to transmit movement the relative angular positions of saidcrank-member and said crankshaft will differ in all cases by an anglewhich is a multipl of and that when said crank-pin passes through itsdead centre at the end of said one half of a revolution of thecrank-member, one of the cylinders will be about to attain the end ofthe compression period of the cycle.

. 5. A turning gear for turning the crankshaft of a two-stroke internalcombustion engine having N cylinders with a view of starting saidengine, comprising operating means, a rotatable crank-member in the formof a circular gear carrying an eccentric crank-pin, a connecting meansbetween said operating means and said crank-member for rotating samefrom said operating means, spring means connected to said crank-pin andexpanding during one half of a revolution ofsaid crank-member andcontracting during the other half revolution of said crank-memberthereby imparting an additional impulse to said crankshaft, a speedreducing transmission for connecting said crank-member to the crankshaftto be turned so that the ratio between the angles described by saidcrank member and said crankshaft during the starting operation will beequal to N, and uncoupling means

